High Key / Low Key are more terms related to the composition of tones, than to a specific development technique. If you have a white on white subject, that's high key. If you have a black on black, that's low key.
In B&W, provided that you have proper exposure, high key scenes and low key scene will print more or less the same.
What you might want to do is think about your metering technique in a situation that is not inherently high/low key. For example, if you are in a room lit by a bright window only, and someone is between your camera and the light source (i.e. a backlit portrait situation) you could achieve a low key effect by deliberately underexposing the shadow area, leaving only the brightest highlights as white. You could also achieve a high key effect by overexposing the same area: the person's face will end up near white, and the background will be pure white.
In Zonie terms: you have a scene before you that has a very great subject brightness ratio. If you put the brightest part of the scene on Zone VIII, most of the picture will fall below Zone III, and thus leave you with large areas of featureless, solid shadows. If you put instead the less bright part of the scene on Zone VI or VII, you will have an entire scene above Zone V, thus high key.